Crystal and molecular structures of the Rh[(C2H5O)2PS2]3 and Co[(C6H5O)2PS2]3 chelate compounds

The crystal structures of the Rh[(EtO)₂PS₂]₃ (I) and Co[(PhO)₂PS₂]₃ (II) chelate compounds were determined from X-ray diffraction (XRD) data (CAD-4 diffractometer, MoK _β radiation, 1193 F _hkl , R = 0.0516 for I and 513 F _hkl , R = 0.0305 for II). Crystals I are monoclinic: a = 14.233(3) Å, b = 13.570(3) Å, c = 14.272(3) Å; β = 90.66(3)°, V = 2756.3(10) ų, Z = 4, ρ_calc = 1.587 g/cm³, space group C2/c. Crystals II are trigonal: a = 15.149(2) Å, c = 30.306(6) Å; V = 6023.2(16) ų, Z = 6, ρ_calc = 1.493 g/cm³, space group R3ˉ. Structures I and II consist of discrete mononuclear molecules. The coordination polyhedra of the M atoms (M = Rh, Co) are distorted octahedra formed by six sulfur atoms of three cyclic bidentate (RO)₂ PS₂⁻ ligands. Original Russian Text Copyright ? 2008 by R. F. Klevtsova, L. A. Glinskaya, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 2, pp. 330–334, March–April, 2008.     

Elektrochemische Synthese von Perowskiten im System K/Ba/Pr/Bi/O

Electrochemical Synthesis of Perovskites in the System K/Ba/Pr/Bi/O An easy procedure for the synthesis of well crystalline samples of (K,Ba)(Pr,Bi)O₃ is provided by anodic oxidation of melts consisting of Ba(OH)₂ / KOH / Pr(NO₃)₃ / Bi(NO₃)₃, at comparatively low temperatures of about 220 °C. We have explored the influence of different parameters like temperature, potential of the working electrode, and composition of the electrolyte. Chemical and thermal analyses were performed. Products obtained at different experimental conditions revealed different Ba/K and Pr/Bi ratios with a large homogeneity range. X‐Ray powder diffraction and single crystal structure analyses of K_xBa_1?xPr_yBi_1?yO₃ proved these compounds to be cubic perovskites. Barium and potassium ions are disordered occupying the A‐sites while praseodym and bismuth ions share the B‐sites or are ordered, as indicated by a doubling of the lattice parameter. The composition x and y can independently be altered. XPS analysis and physical properties are reported and discussed.     

Preparation of chiral diimino- and diaminodiphosphine ligands and their Cu and Ag complexes. X-ray crystal structures of [Cu(1S,2S-cyclohexyl-P2N2)][PF6] and [Ag(1R,2R-cyclohexyl-P2N2H4)][BF4]

The interaction of optically pure 1R,2R-diammoniumyclohexane mono-(+)-tartrate and 1S,2S-diammoniumcyclohexane mono-(−)-tartrate with 2 equiv. of o-(diphenylphosphino)benzaldehyde in the presence of 2 equiv. of potassium carbonate in a refluxing ethanol/water mixture gave the optically pure condensation products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diiminocyclohexane[1R,2R-cyclohexyl-P₂N₂, (R,R)-I] and N,N′-bis[o-(diphenylphosphino)benzylidene]-1S,2S-diiminocyclohexane [1S,2S-cyclohexyl-P₂N₂, (S,S)-I], respectively, in good yield. Reduction of optically pure (R,R)-I and (S,S)-I with NaBH₄ in ethanol gave the optically pure reduced products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diaminocyclohexane[1R,2R-cyclohexyl-P₂N₂H₄, (R,R)-II] and N,N′-bis[o-diphenylphosphine)benzylidene]-1S,2S-diaminocyclohexane[1S,2S-cyclohexyl-P₂N₂H₄, (S,S)-II], respectively, in good yield. The coordination behaviour of I and II toward salts of Cu^I and Ag^I have been examined. The interaction of [Cu(C)₃CN)₄][X] (X = ClO₄⁻, PF₆⁻) with 1 equiv. of optically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II] gave the corresponding optically pure [CuL₄][X] complexes, III–VI IIIa, L₄ = (R,R)-I, X = PF₆⁻ IIIb, L₄ = (R,R)-I, X = ClO₄⁻ IV, X = PF₆⁻; Va, L₄ = (R,R)-II, X = PF₆⁻, Vb L₄ = (R,R)-II, X= ClO₄⁻, VI L₄ = (S,S)-II, X = PF₆⁻, in good yield. For the Cu^I complexes, the L₄ ligand acted as a tetradentate ligand. However, a variable-temperature ³¹P[¹H] NMR study of IIIb shows that at ambient temperature one of the imino groups of the tetradentate ligand undergoes rapid dissociation to form a tridentate ligand. The interaction of AgBF₄ with 1 equiv. of otpically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II gave the corresponding optically pure [AgL₄][BF₄] complexes, VII–X VII L₄ = (R,R)-I; VIII, L₄ = (S,S)-I; IX,L₄ = (R,R)-II; X, L₄ = (S,S)-II], in good yield. For the Ag^I complexes, the L₄ ligand acted as a tetradentate ligand with the two amino groups coordinated unsymmetrically to the silver. A variable temperature ³¹P [¹H] NMR study of VII suggests that at high temperature the complex exists as a tri-coordinated complex. The structurers of IV and IX were established by X-ray diffraction studies.     

一个新颖的三维异核锑(III)-镨(III)配合物[Sb2-μ4-(EDTA)2Pr(H2O)5]NO3•4H2O的合成、晶体结构及热分解研究

合成了锑-镨与乙二胺四乙酸形成的新颖三维配合物[Sb₂-μ₄-(EDTA)₂Pr(H₂O)₅]NO₃•4H₂O, 用元素分析、红外光谱、热分析及X射线单晶衍射法等进行了组成和结构表征. 结果表明该配合物属正交晶系, 空间群Pnn2; 晶胞参数: a＝1.07031(2) nm, b＝2.30805(4) nm, c＝0.72343(2) nm, V＝1.78711(7) nm³, Z＝2, D_c＝2.202 g/cm³, F(000)＝1164, μ＝2.955 mm^－1, GOF＝1.000, 最终偏离因子R₁＝0.0203, wR₂＝0.0545 [I＞2σ(I)]. 在标题化合物中, 每个镨(III)离子的配位数为9, 与五个水分子中的五个氧原子和四个羧基氧原子配位, 形成三帽三角棱柱空间配位多面体. 锑(III)与EDTA离子中的四个氧原子和两个氮原子配位, 在赤道平面上有一孤对电子. 同时讨论了配合物的热分解过程.     

Two New Octahedral Cd(II) Complexes [Cd(L)2] and {[Cd(LH)2(SCN)2]H2O} [L = C6H5C(OH)NN = C(CH3)C5H4N]: Synthesis and Structural Studies

Two new octahedral Cd(II) complexes [Cd(L)₂] (1) and {[Cd(LH)₂(SCN)₂]H₂O} (2) [where LH = C₁₄H₁₃N₃O] are synthesized using a tridentate hydrazone ligand (LH) and they are characterized by elemental analysis, IR spectra, NMR spectra, thermal studies and finally the structures have been determined by single crystal X-ray diffraction. Complex 1 crystallizes in monoclinic system, space group C2/c with a = 22.565(6) ?, b = 10.252(3) ?, c = 12.187(4) ?, β = 118.851(2)^∘, and Z = 4. Complex 2 also crystallizes in the monoclinic system, space group P2₁/c with a = 9.257(9)?, b = 17.809(2)?, c = 9.548(9)?, β = 107.439(4)^∘, and Z = 2. In 1 the ligand binds the Cd(II) ion in tridentate fashion, whereas in 2 it acts as a bidentate ligand.     

细胞内不同形态Gd基MRI造影剂的T1/T2弛豫性能及造影效果

将具有良好生物膜穿透性的异烟肼(INH)和Gd-DO3A偶联,合成了小分子MRI造影剂Gd-DO3A-INH;利用脉冲电转染技术标记间充质干细胞,有效提高了进入细胞的Gd-DO3A-INH浓度,并诱导部分游离态Gd-DO3A-INH在细胞质中自组装成纳米粒子。细胞样品的TEM观察到细胞内形成了Gd-DO3A-INH纳米粒子;细胞传代实验和体外MRI揭示了2种不同状态的Gd-DO3A-INH对细胞水质子弛豫速率的影响机制,以及细胞传代过程中细胞内2种不同状态Gd-DO3A-INH的浓度涨落引起的MRI造影效果的变化机制。     

Metal–Organic Frameworks-Derived Mesoporous Si/SiOx@NC Nanospheres as a Long-Lifespan Anode Material for Lithium-Ion Batteries

Silicon (Si)-based anode materials with suitable engineered nanostructures generally have improved lithium storage capabilities, which provide great promise for the electrochemical performance in lithium-ion batteries (LIBs). Herein, a metal–organic framework (MOF)-derived unique core–shell Si/SiO_x@NC structure has been synthesized by a facile magnesio-thermic reduction, in which the Si and SiO_x matrix were encapsulated by nitrogen (N)-doped carbon. Importantly, the well-designed nanostructure has enough space to accommodate the volume change during the lithiation/delithiation process. The conductive porous N-doped carbon was optimized through direct carbonization and reduction of SiO₂ into Si/SiO_x simultaneously. Benefiting from the core–shell structure, the synthesized product exhibited enhanced electrochemical performance as an anode material in LIBs. Particularly, the Si/SiO_x@NC-650 anode showed the best reversible capacities up to 724 and 702 mAh g⁻¹ even after 100 cycles. The excellent cycling stability of Si/SiO_x@NC-650 may be attributed to the core–shell structure as well as the synergistic effect between the Si/SiO_x and MOF-derived N-doped carbon.     

Synthesis and characterization of methylpalladium(II) dithiolate complexes of the type [PdMe(SS)(ER3)] (SS = S2CNR 2, S2COEt, S2P(OR)2, S2 PPh2; ER3 = PMePh2, PPh3, AsPh3)

Methylpalladium(II) dithiolate complexes of the type [PdMe(SS)(ER₃] (SS = S₂ CNR₂ (R = Me or Et), S₂COEt, S₂P(OR)₂ (R = Et, ⁿPr, ⁱPr), S₂PPh₂; ER₃ = PMePh₂, PPh₃, AsPh₃) have been synthesized by the reaction of [Pd₂Me₂(μ-Cl)₂(PMePh₂)₂] with sodium/potassium/ammonium salts of the dithio acid or by treatment of [PdMeCl(cod)] with ER₃ followed by sodium/potassium/ammonium salts of the dithio ligand. All the complexes were characterized by elemental analysis, IR and nuclear magnetic resonance (¹H, ³¹P) data.     

Ag/PANI/Fe_2O_3复合纳米粒子的合成与催化性能

借助于PANI的还原性质,PANI/Fe2O3复合载体与AgNO3发生表面氧化还原反应,合成了Ag/PANI/Fe2O3复合纳米粒子。TEM和XRD结果表明,立方晶系纳米银的平均粒径10nm。FTIR结果表明,Ag与PANI及Fe2O3复合载体之间不存在化学键合作用,但由于PANI与Ag之间的电子相互作用,Ag/PANI/Fe2O3复合纳米粒子的FTIR吸收峰发生蓝移。Ag/PANI/Fe2O3复合纳米粒子对于间硝基苯磺酸钠的硼氢化钠还原反应表现出良好的催化活性,30min内间硝基苯磺酸钠的转化率达到86.77%。     

RECTIFYING EFFECT OF POLYANILINE(PANI)/N-TYPE POROUS SILICONE HETEROJUNCTION*

Heterojunctions between polyaniline (PANI) and n-type porous silicon (PS), Al/PS-PANI/Au cell,were fabricated, and the rectifying parameters of this heterojunction diode were measured as a function of thepreparation conditions of PANI and PS, the electronic structure of PANI as well as cell structure. Therectifying parameters of Al/PS-PANI/Au cell were determined to be γ= 1 .8×10~1～ 1 .0×10~5 for the rectifyingratio at 3V, n = 3 ～12 for the ideal factor,j_0 = 8.0×10~(-5)～5.6×10~(-2) mA/cm~2 for the reversed saturated currentdensity, and φ_b = 0.67～ 0.83 V for the barrier height, respectively. The best rectifying heterojunction diodemade between PANI and n-type PS with higher rectifying factor (γ= 1 .0×10~5 at 3V ), output current (>1500mA/cm~2 at 3V) and lower ideal factor (n = 3.3) was obtained by preventing the oxidation of PS beforeevaporating Al electrode.     

Synthesis and crystal and molecular structure of CdPhen( iso -C4H9OCS2)2 and CdPhen( n -C4H9OCS2)2 mixed-ligand complexes

Mixed-ligand complexes CdPhen(i-BuOCS₂)₂ (I) and CdPhen(n-BuOCS₂)₂ (II) have been synthesized. Their structures were solved using X-ray diffraction data (X8 APEX diffractometer, MoK _α radiation, 1641 and 2497 F _hkl , R = 0.0359 and 0.0389). Crystals I are orthorhombic with unit cell parameters a = 6.5883(3) Å, b = 19.7123(10) Å, c = 20.1936(11) Å, V = 2622.6(2) ų; Z = 4, space group Pbcn; crystals II are monoclinic, a = 6.5845(2) Å, b = 19.1522(6) Å, c = 20.7091(7) Å, β = 97.106(1), V = 2591.5(1) ų, Z = 4, space group C2/c. The structures consist of discrete mononuclear molecules in which the coordination polyhedron of the Cd atom is a distorted N₂S₄ octahedron. Molecular packing and interactions in the structures are discussed. Original Russian Text Copyright ? 2007 by R. F. Klevtsova, T. G. Leonova, L. A. Glinskaya, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 2, pp. 274–281, March–April, 2007.     

One-dimensional structures of zinc(II) and cobalt(II) coordination complexes [Zn(NCS)2(PPz)]n and [CoCl2(PPz)]n (PPz=piperazine)

The reaction of Zn(NO₃)₂·6H₂O with PPz hexahydrate (PPz=piperazine) and NH₄SCN in CH₃OH afforded the complex [Zn(NCS)₂(PPz)]_n (1). The reaction of CoCl₂·6H₂O with PPz in CH₃OH afforded the complex [CoCl₂(PPz)]_n (2). The PPz ligand in 1 is coordinated to the metal centers through both nitrogen atoms to form a 1-D zigzag-chain structure and the distorted tetrahedral coordination geometry at each zinc center is completed by a pair of N-bonded thiocyanate ligands. Compound 2 has an analogous 1-D zigzag-chain structure containing terminal chloro ligands. Important NCSH---N hydrogen-bonding interactions in compound 1 and N---HCl---M and C---HCl---M hydrogen-bonding interactions in compound 2 play a significant role in aligning the polymer strands in the crystalline solid.     

配合物[Pd(phen)Cl2]与腺嘌呤的键合作用研究

合成并表征了固体三元配合物[Pd(phen)Cl₂] 1. 以1和DNA的组成小分子腺嘌呤(ade)反应, 获得双核配合物单晶[Pd₂(phen)₂(ade)₂]Cl₂•4.5H₂O (2). 配合物2为正交晶系, 空间群为Pnma, 晶胞参数a＝2.1709(9) nm, b＝1.4378(6) nm, c＝1.2274(5) nm, α＝β＝γ＝90°, V＝3.8311(3) nm³, D_c＝1.729 g/cm³, Z＝4, F(000)＝2004, R₁＝0.0766, wR₂＝0.1526. phen配体以两个氮原子与钯(II)离子配位, 按生物学原子规范标号, ade以N(3), N(9)原子与钯(II)离子桥联配位, 形成双核混配型配合物.     

Preparation and characterization of polypropylene/mesoporous silica nanocomposites with confined polypropylene

Polypropylene (PP)/Ti-MCM-41 nanocomposites were prepared by isospecific propylene polymerization with Ti-MCM-41/Al(i-C₄H₉)₃ catalyst. The cross polarization/magic angle spinning (CP/MAS) ¹³C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti-MCM-41 in the nanocomposites, as measured by N₂ adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti-MCM-41. Alkali treatment followed by extraction with o-dichlorobenzene allows us to extract the confined PP out of the Ti-MCM-41 mesopores. Although the PP/Ti-MCM-41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (M_w) and molecular weight distribution (M_w/M_n) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti-MCM-41 mesopores (M_w = 200,000–450,000, M_w/M_n = 40–75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324–3332, 2003     

Theoretical study on the structures and properties of the isomers of Nn(CH)8−nH8 (n = 0–7)

With replacement of N atoms by CH groups in the most stable chain isomer of N8H8, 34 possible isomers of N_n(CH)_8−nH₈ (n = 0–7) have been designed and optimized at the B3LYP/6-311++G** level of theory. The natural bond orbital (NBO) and atoms in molecules (AIM) analysis are carried out to study the bonding nature and relative stabilities of these conformers. G3MP2 method is applied to calculate energies and heats of formation. The results indicate that the hyperconjugation effect from lone pairs of nitrogen atoms to germinal C–N bonds is the major factor which caused the change of the C–N bond length. With the more replacement of nitrogen atoms by CH groups, the heats of formation of the isomers of N_n(CH)_8−nH₈ (n = 0–7) decrease gradually, but the energies increase linearly.     

Neue Tetrapnictidotitanate(IV): Na3M3[TiX4] mit M  Na/Sr,Na/Eu und X  P,As

New Tetrapnictidotitanates(IV): Na₃M₃[TiX₄] with M ? Na/Sr, Na/Eu and X ? P, As The four novel tetrapnictidotitanates(IV) Na₄Sr₂TiP₄, Na₄Sr₂TiAs₄, Na_4.3Eu_1.7TiP₄ and Na_4.3Eu_1.7TiAs₄ were prepared from the binary pnictides NaX, M₃X, M′X (X ? P, As and M′ ? Sr, Eu) and elementary titanium in tantalum ampoules. The air and moisture sensitive transition metal compounds form dark red hexagonal crystals. They are semiconductors with E_g = 1.8eV (Sr) and E_g = 1.3eV (Eu), respectively. The compounds are isotypic with Na₆ZnO₄ (space group P6₃mc (no. 186); hP22; Z = 2; Na₄Sr₂TiP₄; a = 936.8(1) pm, c = 740.5(1) pm; Na₄Sr₂TiAs₄: a = 958.2(1) pm, c = 757.1(1) pm; Na_4.3Eu_1.7TiP₄: a = 929.9(2) pm, c = 732.0(2) pm; Na_4.3Eu_1.7TiAs₄: a = 953.9(1) pm, c = 749.5(1) pm). Main structural units are polar oriented [TiP₄]^8? and [TiAs₄]^8? tetrahedral anions with d (Ti? P) = 240.2(3) pm and d (Ti? As) = 248.6(3) pm.     

Mass transfer from theophylline hydrogels of a‐PVA/H2O and a‐PVA/NaCl/H2O system on heating

Theophylline hydrogels of atactic‐poly(vinyl alcohol) (a‐PVA)/H₂O and a‐PVA/NaCl/H₂O systems were prepared followed by cyclic freezing (?30°C for 16 hr)–thawing (at room temperature for 8 hr) and one cycle gelation (at ?20°C for 24 hr) processes, respectively. In order to prepare xerogels (dried hydrogels) of these hydogel systems, an apparently first‐order mass transfer phenomenon of water as evaporation was observed for a‐PVA/H₂O hydrogel system, while heating at 60°C. The rate of evaporation decreased with increasing time in hyperbolic fashion. The total surface area (both lateral and two end surfaces of hydrogel matrix disc) decreased linearly for the first 90 min and thereafter had a tendency towards the steady‐state. The total mass flux showed time dependent linear reduction phenomenon, which is a characteristic physical behavior for these hydrogel systems on heat treatment. When NaCl was included in a‐PVA/H₂O system mass transfer of water followed fourth‐order polynomial. But in consideration of a comparative study, sustained mass transfer was found from the hydrogel matrices of a‐PVA/H₂O/NaCl system (gelation at ?20°C). Copyright © 2003 John Wiley & Sons, Ltd.     

Crystal and molecular structure of the [Y(Phen){( i -C4H9)2PS2}2NO3] mixed-ligand compound

The [Y(Phen){(i-C₄H₉)₂PS₂}₂NO₃] mixed-ligand compound (I) was synthesized. Its structure was determined by X-ray diffraction analysis (X8 APEX diffractometer, λMoK _α , 3788 F _hkl , R = 0.0677). Crystals I are orthorhombic: a = 10.6495(8) Å, b = 20.006(2) Å, c = 35.317(4) Å, V = 7524.4(13) ų, Z = 8, ρ_calc = 1.324 g/cm³, space group Pbca. The structure is built of mononuclear discrete molecules. The N₂O₂S₄ coordination polyhedron of the Y atom is a distorted dodecahedron. Original Russian Text Copyright ? 2008 by V. L. Varand, L. A. Glinskaya, R. F. Klevtsova, and S. V. Larionov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 49, No. 1, pp. 182–186, January–February, 2008.     

Spin Crossover Properties of the [Fe( PM - BiA )2(NCS)2] Complex – Phases I and II

Summary.  In the present review, we reexamine the photomagnetic properties of the [Fe(PM-BiA)₂(NCS)₂], cis-bis(thiocyanato)-bis[(N-2′-pyridylmethylene)-4-(aminobiphenyl)]iron(II), compound which exhibits, depending on the synthetic method, an exceptionally abrupt spin transition (phase I) with a very narrow hysteresis (T _1/2↓ = 168 K and T _1/2↑ = 173 K) or a gradual spin conversion (phase II) occurring at 190 K. In both cases, light irradiation in the tail of the ¹MLCT-LS absorption band, at 830 nm, results in the population of the high-spin state according to the light-induced excited spin-state trapping (LIESST) effect. The capacity of a compound to retain the light-induced HS information, estimated through the T(LIESST) experiment, is determined for both phases. Interestingly, the shape of the T(LIESST) curve is more gradual for the phase II than for the phase I and the T(LIESST) value is found considerably lower in the case of the phase II. The kinetics parameters involved in the photoinduced high-spin→low-spin relaxation process are estimated for both phases. From these data, the experimental T(LIESST) curves are simulated and the particular influence of the cooperativity as well as of the parameters involved in the thermally activated and tunneling regions are discussed. The Light-Induced Thermal Hysteresis (LITH), originally described for the strongly cooperative phase I, is also reinvestigated. The quasi-static LITH loop is determined by recording the photostationary points in the warming and cooling branches. Corresponding authors. E-mail: letard@icmcb.u-bordeaux.fr Received August 26, 2002; accepted August 30, 2002     

Structural and magnetic properties of CoxZn1−xFe2O4 nanocrystals synthesized by microwave method

Microwave assisted combustion method was used to produce nanocrystalline cobalt doped zinc ferrite, Co_xZn_1−xFe₂O₄, from stoichiometric mixture of (Co(NO₃)₂·6H₂O), (Fe(NO₃)₃·9H₂O), (Zn(NO₃)₂·6H₂O), and urea (CO(NH₂)₂) as a fuel. The structural, morphological and magnetic properties of the products were determined by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) respectively. The average crystallite sizes obtained from XRD were between 35 and 39 nm. Magnetization measurements indicate that samples with less Co content have superparamagnetic behavior at room temperature. When the Co substitution increases the saturation magnetization due to the magnetic character of the Co cations substituting the non-magnetic Zn and coercivity also increase due to anisotropic nature of cobalt. The Co_xZn_1−xFe₂O₄ nanocrystals exhibit typical features of an assembly of magnetic particles with a distribution of blocking temperatures and indicate the spin-glass behavior.